In a DC motor, it is important to place the brushes along ______ A) Magnetic Neutral Axis B) Normal Geometric Axis C) Nominal Geometric Axis D) None of these
Last Answer : In a DC motor, it is important to place the brushes along Magnetic Neutral Axis
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Apr 29, 2018
by
anonymous

From which material field coils of DC generator are made of?
Last Answer : Field coils of DC generator are usually made of copper.
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118 views
1 answer
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Mar 3, 2018
by
anonymous

Last Answer : Brushes of D.C. machines are made of carbon.
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1 answer
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Mar 20, 2018
by
anonymous

A 200 V DC machine supplies 20 A at 200 V as a generator. The armature resistance is 0.2 Ohm. If the machine is now operated as a motor at same terminal voltage and current but with the flux increased by 10%, the ratio of motor speed to generator speed is
Last Answer : A 200 V DC machine supplies 20 A at 200 V as a generator. The armature resistance is 0.2 Ohm. If the machine is now operated as a motor at same terminal voltage and current but with the flux increased by 10%, the ratio of motor speed to generator speed is 0.87
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1 answer
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May 8, 2018
by
anonymous

A 36 slot, 4 -pole, dc machine has a simplex lap winding with two conductors per slot. The back pitch and front pitch adopted could be respectively
Last Answer : A 36 slot, 4 -pole, dc machine has a simplex lap winding with two conductors per slot. The back pitch and front pitch adopted could be respectively 19,17
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1 answer
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May 3, 2018
by
anonymous

The induced emf in the armature of a lap -wound four -pole dc machine having 100 armature conductors rotating at 600 rpm and with 1 Wb flux per pole is (1) 1000V (2) 100V (3) 600V (4) 10,000V
Last Answer : The induced emf in the armature of a lap -wound four -pole dc machine having 100 armature conductors rotating at 600 rpm and with 1 Wb flux per pole is 1000V
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Apr 29, 2018
by
anonymous
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Aluminium is not used as winding wire for the armature of a dc machine because (1) aluminium has low resistivity (2) a large winding space is taken by aluminium conductors and creates ... ) the thermal conductivity of aluminium is low (4) aluminium has low conductivity as compared to copper
Last Answer : Aluminium is not used as winding wire for the armature of a dc machine because (2) a large winding space is taken by aluminium conductors and creates jointing problems (3) the thermal conductivity of aluminium is low (4) aluminium has low conductivity as compared to copper
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Apr 29, 2018
by
anonymous
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In a dc machine, interpoles are used to (1) neutralize the effect of armature reaction in the interpolar region (2) generate more induced emf in the armature (3) avoid interference of the armature flux with the main -field flux (4) reduce the demagnetizing effect of armature reaction
Last Answer : In a dc machine, interpoles are used to neutralize the effect of armature reaction in the interpolar region
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Apr 29, 2018
by
anonymous

Why poles of dc machine are laminated?
Last Answer : Poles of DC machines are laminated to reduce the eddy current losses in the poles.
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112 views
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Apr 27, 2020
by
anonymous

Last Answer : Copper losses,iron losses,variable losses , constant losees
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1 answer

Explain concept of back emf in DC machine. State how it governs armature current.
Last Answer : Back emf: When the armature of DC machine rotates under the influence of driving torque, the armature conductors move in the magnetic field and cut it and hence emf is induced in them. The ... flow of armature current i.e. it automatically changes the armature current to meet load requirements.
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asked
Jul 27, 2019
by
anonymous

The magnetic neutral plane shifts in a dc machine (A) in the direction of motion of motor (B) in the direction of motion of generator (C) due to increase in the field flux (D) cause reduction of flash over between commutator segments
Last Answer : The magnetic neutral plane shifts in a dc machine in the direction of motion of generator
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162 views
1 answer
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Apr 28, 2018
by
anonymous

What is the percentage of stray losses in DC machine?
Last Answer : Percentage of stray losses in DC machine is about 1 % .
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1 answer
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Mar 8, 2018
by
anonymous

Last Answer : Iron loss, copper loss and mechanical losses these are the losses in DC machine.
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118 views
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Sep 27, 2017
by
anonymous

Last Answer : Copper brushes in D.C. machine are used where low voltage and high currents are involved.
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Mar 20, 2018
by
anonymous

Last Answer : In a D.C. machine stray loss is the sum of iron loss and mechanical loss.
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1 answer
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Mar 21, 2018
by
anonymous

Last Answer : To avoid formation of grooves in the commutator of a D.C. machine the brushes of opposite polarity should track each other.
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3.0k views
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Mar 21, 2018
by
anonymous

Last Answer : Open circuited armature coil of a D.C. machine is identified by the scarring of the commutator segment to which open circuited coil is connected and indicated by a spark completely around the commutator.
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1 answer
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Mar 20, 2018
by
anonymous

Last Answer : In case of D.C. machine winding, number of commutator segments is equal to number of armature coils.
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1 answer
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Mar 20, 2018
by
anonymous
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84 views
0 answers
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Mar 20, 2018
by
anonymous

Last Answer : Iron losses in a D.C. machine are independent of variations in load.
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1 answer
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Mar 20, 2018
by
anonymous

Last Answer : In a four-pole D.C. machine alternate poles are north and south.
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1 answer
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Mar 20, 2018
by
anonymous

Last Answer : The rapid wear of brushes takes place due to abrasion from dust, excessive spring pressure, rough commutator bars, high mica insulation between com-mutation bars.
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Mar 21, 2018
by
anonymous

Last Answer : Armature coil is short circuited by brushes when it lies along neutral axis.
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Mar 21, 2018
by
anonymous

Last Answer : The number of brushes in a commutator depends on amount of current to be collected.
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158 views
1 answer
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Mar 20, 2018
by
anonymous

Last Answer : The material for commutator brushes is generally carbon.
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1 answer
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Mar 20, 2018
by
anonymous

Last Answer : In lap winding, the number of brushes is always same as the number of poles.
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Mar 20, 2018
by
anonymous

Last Answer : The rotor of a hysteresis motor is made of chrome steel.
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Mar 20, 2018
by
anonymous

UNIT 1 fundamentals of AC rotating machine Contents 1.1 Introduction 1.2 Advantages 1.3 Parts of AC machines 1.4 Synchronous speed 1.5 AC winding 1.6 Winding factor ( ... alternator or generator 1.9 Numericals 1.10 Harmonic 1.11 Slot harmonics 1.12 Harmonics minimization
Last Answer : 1.2 Advantages: In practices most of alternator have rotating magnetic field type construction with stationary armature due to following reason. The generation level of AC voltage may be in the range ... at high speed. Only two Slip rings are required to excited the field by AC supply.
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Aug 25, 2018
by
Notes

Analyze the differences of FOC and DTC. The switching frequency of FOC is 1.3 kHz and the average switching frequency of DTC is the same.
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In a synchronous machine, if the field flux axis ahead of the armature field axis in the direction of rotation, the machine is operating as (1) synchronous motor (2) synchronous generator (3) asynchronous motor (4) asynchronous generator
Last Answer : In a synchronous machine, if the field flux axis ahead of the armature field axis in the direction of rotation, the machine is operating as synchronous generator
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1 answer
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May 1, 2018
by
anonymous

The armature current on symmetrical 3 phase short circuit of a synchronous machine (salient pole) (A) has q -axis current only (B) has d -axis current only (C) has both d and q axis currents (D) cannot be divided between q and d axis currents
Last Answer : The armature current on symmetrical 3 phase short circuit of a synchronous machine (salient pole) has d -axis current only
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Apr 29, 2018
by
anonymous

Torque angle for the synchronous machine is the angle between (A) stator magnetic field and rotor magnetic field (B) stator magnetic field and net magnetic field in the air gap (C) rotor magnetic field and net magnetic field in the air gap (D) excitation voltage and impedance voltage drop
Last Answer : Torque angle for the synchronous machine is the angle between rotor magnetic field and net magnetic field in the air gap
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Apr 28, 2018
by
anonymous

In DC generators lamination core are generally made of?
Last Answer : In DC generators lamination core are generally made of silicon steel.
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Mar 3, 2018
by
anonymous

I got some grapic drawing questions guys and I need to see the answers immediately.Stator voltage curve for each four different start up methods.
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Describe the reason of using dc series motor for electric trains.
Last Answer : Electric trains require an inverse torque speed characteristics for proper operation. That is a higher torque is required at start (when speed is nil or low) and as the train picks up ... torque - speed characteristics of DC series motors match, these motors are suitable for electric trains
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1 answer
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Sep 18, 2018
by
anonymous

A 240 V, dc shunt motor draws 15 A while supplying the rated load at a speed of 80 rad/s. The armature resistance is 0.5 W and the field winding resistance is 80 W. The net Voltage across armature resistance at the time of plugging will be
Last Answer : A 240 V, dc shunt motor draws 15 A while supplying the rated load at a speed of 80 rad/s. The armature resistance is 0.5 W and the field winding resistance is 80 W. The net Voltage across armature resistance at the time of plugging will be 474 V
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May 8, 2018
by
anonymous

A 200 V dc shunt motor is running at 1000 rpm and drawing a current of 10 A. Its armature winding resistance is 2 Ohm. It. is braked by plugging. The resistance to be connected in series with armature to restrict armature current to 10 A, is
Last Answer : A 200 V dc shunt motor is running at 1000 rpm and drawing a current of 10 A. Its armature winding resistance is 2 Ohm. It. is braked by plugging. The resistance to be connected in series with armature to restrict armature current to 10 A, is 36 Ohm
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332 views
1 answer
asked
May 3, 2018
by
anonymous

The fall in speed of a dc generator due to increase in load can be corrected by (1) cooling the armature.. (2) increasing the excitation. (3) reducing the load voltage. (4) increasing the input to the prime mover
Last Answer : It can be corrected by increasing the input to the prime mover.
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355 views
2 answers
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May 1, 2018
by
anonymous
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In dc machines, the armature windings are placed on the rotor because of the necessity for (1) electromechanical energy conversion (2) generation of voltage (3) commutation (4) development of torque
Last Answer : 3 Commutation
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2 answers
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May 1, 2018
by
anonymous

Identify the increasing order of voltage regulation of the following dc generators a same load : (A) differential compound, shunt and under compound (B) shunt, differential compound and ... C) under compound, shunt and differential compound (D) shunt, under compound and differential compound
Last Answer : Identify the increasing order of voltage regulation of the following dc generators a same load : under compound, shunt and differential compound
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1 answer
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Apr 30, 2018
by
anonymous
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In a 2 kW, 200 V, 1000 rpm. DC series motor the torque at full load was found to be 0.3 N -m. The torque at half full load in N -m is :
Last Answer : In a 2 kW, 200 V, 1000 rpm. DC series motor the torque at full load was found to be 0.3 N -m. The torque at half full load in N -m is : 0.075
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109 views
1 answer
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Apr 29, 2018
by
anonymous

In a DC generator the windings of interpoles are connected : (A) in series with main field winding, to create a pole,of same polarity as the main pole ahead in the direction of rotation. ... winding, to create a pole of opposite polarity as the main pole ahead in the direction of rotation.
Last Answer : In a DC generator the windings of interpoles are connected : in series with the armature winding, to create a pole of same polarity as the main pole ahead in the direction of rotation.
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1 answer
asked
Apr 29, 2018
by
anonymous

The function of a brush and commutator arrangement in a dc motor is to (1) produce unidirectional torque (2) produce unidirectional current in the armature (3) help in changing the direction of rotation of the armature (4) reduce sparking
Last Answer : The function of a brush and commutator arrangement in a dc motor is to produce unidirectional torque
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2.5k views
1 answer
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Apr 29, 2018
by
anonymous
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What is the difference between an AC and DC generator?
Last Answer : The generator which generates DC voltage is called DC generator and generator which generates AC voltage is called AC generator (or) Alternator. In DC generator armature is rotated and field winding ... generator. A DC generator can generate low voltages but an AC generator can generate upto 11kv.
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1 answer
asked
Mar 15, 2018
by
anonymous

What is the RPM of a DC motor?
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0 answers
asked
Mar 15, 2018
by
anonymous

What is the principle of DC generator?
Last Answer : principle
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1 answer
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Mar 15, 2018
by
anonymous

Why is the armature of DC generator laminated?
Last Answer : The armature of DC generator is laminated to reduce eddy current losses.
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176 views
1 answer
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Mar 3, 2018
by
anonymous

What are the speed control methods of dc motor?
Last Answer : Field control of DC motor Armature control of DC motor
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2 answers
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Dec 16, 2017
by
anonymous

Last Answer : Induction motor is a AC motor it is also known as asynchronous motor .
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Sep 9, 2017
by
anonymous
